In No Laying Up’s coverage of the 125th U.S. Open at Oakmont, the Big Man himself introduced a metric that has lodged itself in my brain: the Proper Test Index (PTI). It’s defined as
\[ PTI = \frac{\text{Number of rounds with a score >= 80}}{\text{Number of rounds with a score of < 70}} \]
He ran through some of the numbers across past U.S. Opens, but what does it look like when we extend the metric to the PGA Tour? Using Data Golf’s API, I pulled historical scoring data and calculated the event-level PTI:
A few things stood out to me.
- The pros are really good. Across the entire dataset, only 1.0% of rounds have a score of 80 or over. That’s compared to a healthy 37.2% of rounds falling in the 60s (or lower!).
- There are 140 events that had 0 rounds of 80 or over.
- What were we doing at the 2019 Wyndham Championship? 332 rounds below 70 and 0 above 80. Not Proper.
Now when it comes to majors…
As much as I like Brooks Koepka, the 2018 PGA Championship at Bellerive CC wasn’t particularly proper. But good news for Big! Phil the Thrill’s unbelievable performance in the 2021 PGA Championship at Ocean Course at Kiawah Island was undeniably a Proper Victory. Soly’s right, we somehow don’t talk about that win enough.
Sabermetrics can help us identify Proper Venues
PTI tells us something about the balance of extreme rounds at the event level. What if we adopt Baseball’s park factor to figure out if a low round really matters?
\[ \text{Course Factor} = \frac{\frac{\text{Total scores >= 80 at the course}}{\text{Total scores < 70 at the course}}}{\frac{\text{Total scores >= 80 at all other courses}}{\text{Total scores < 70 at all other courses}}} \]
The larger the course factor, the more impressive a 65 is! Let’s plot out the course factor across the available venues.
Wow. Course Factor has some range! According to this metric, An above average round at Ocean Course at Kiawah Island is worth 1954 times more than a similarly above average round at Sea Island GC (Seaside). Sure.
We’re seeing the effects of rare events; only 1.0% of rounds come in over 80, so if 8.3% of rounds at Ocean Course at Kiawah Island are over 80 (and only 6.4% below 70), we will see extreme values.
What we need is a monotonic transformation that can compress the scale a bit. Using \(\log\), we can get something a bit more readable.
This chart is more legible. Due to the strict scarcity of rounds in the 80s, we’ll be using a logarithmic transformation of course factor (\(\text{Course Factor}^{*}\)) to convey the relative difficulty of each venue.
Now comes the real question, however: Did Big Cook?
Looking at the distribution of scores across each venue,